Heretofore, as a conductive filler incorporated into resin or the like, there has been known a potassium titanate fiber and titania fiber to which conductivity is afforded by coating the fiber surface with a conductive substance, or by producing oxygen deficiency by means of reductive calcination. Since these fibers are excellent in reinforcing property, dispersibility and conductivity, they are put into practice for uses, such as the prevention of electrification, electromagnetic wave shield, and electrode material.
Meanwhile, in the recent years, fillers having more superior conductivity have been developed which can render the desired conductivity in a smaller amount. One superior method is to subject a titanate fiber to nitriding such that part of or the overall fiber is converted to titanium nitride. This method enables to render high conductivity without impairing the strength of the fiber.
For instance, there are known a method in which a fibrous titania or titania hydrate is heated and reduced at a temperature of 500 to 1000.degree. C. in a reducing atmosphere containing ammonia gas, to obtain a conductive acid titanium nitride fiber (JP-A-215718/1989), and a method in which a potassium titanate fiber is calcinated with heating in an atmosphere of ammonia gas, to obtain a potassium titanate fiber, part of which has been converted to titanium nitride (JP-A-27573/1993).
Unfortunately, both methods have the following drawbacks. That is, since they require heat treatment in an atmosphere of ammonia gas, meticulous care should be taken in avoiding leakage to the surroundings, and it is difficult to adjust the partial pressure of ammonia gas in the atmosphere. Further, in order to obtain a high degree of nitriding, it is necessary to continue the reaction for a long period of time because the reduction reaction proceeds predominantly than the nitriding reaction. This can cause deformation of the starting fiber shape.
Furthermore, the fibers obtained by the above methods have high hardness because part of the fiber surface is directly exposed as titanium nitride. Therefore, when the fiber is used as a filler for resin, it is liable to wear a molding die. Additionally, a resin composition incorporating this fiber is poor in slidability and wear resistance.
An object of the present invention is to provide a conductive powder which is excellent in reinforcing property and conductivity, as well as slidability and wear resistance, and can prevent wear of dies.
Another object of the present invention is to provide a conductive powder having good conductivity which can be prepared at a relatively low temperature and in a short period of time.